Conventional solar cells are constructed with a flat-plate-form structure overall, in which an n type diffusion layer is formed in the surface of a p type semiconductor substrate, a herring-bone-type light receiving surface electrode is formed near the front surface, and a back surface electrode is formed near the back surface. In the case of such flat-plate-form solar cells, when the angle of incidence of sunlight on the solar cell becomes large in the morning or evening, the reflectivity at the surface increases, so that the proportion of the sunlight that enters the interior of the solar cell drops.
In the past, therefore, various types of solar cell panels using solar cells comprising spherical semiconductor cells with a diameter of approximately 1 to 2 mm have been proposed. For example, the inventor of the present application has proposed a solar cell and light emitting device comprising a spherical semiconductor element as indicated in WO 98/15983. In such devices, a diffusion layer, a pn junction and a pair of electrodes positioned on both ends with the center of the single crystal silicon interposed are formed on a spherical p type or n type single crystal of silicon. Numerous solar cells of the abovementioned type are disposed in the form of a matrix that has numerous rows and numerous columns; these cells are connected in series and parallel, and are sealed in embedded form by a transparent synthetic resin, thus producing a solar cell panel. This solar cell is advantageous in that a plurality of solar cells of this type can be connected in series, since a pair of electrodes are formed on both ends of the solar cell. However, it is not easy to arrange a plurality of the solar cells in the form of a matrix, and to connect these numerous solar cells in a series-parallel connection.
For example, the inventor of the present application attempted to dispose a plurality of solar cells in the form of a matrix in a sandwich configuration between two printed boards.
In this case, however, a plurality of solar cells must be precisely positioned on one printed board, and numerous electrodes must be connected; furthermore, another printed board must be superimposed on this assembly, and numerous electrodes must be connected here as well. Accordingly, the structure of the solar cell panel becomes complicated, the size of the panel is increased, and the cost of parts and cost of assembly are increased, so that the manufacturing cost of the solar cell panel is increased.
Here, panels with various types of structures have been proposed as solar cell panels in which numerous spherical solar cells are disposed in the form of a matrix.
A solar cell panel in which numerous solar cells are connected in parallel via two sheets of aluminum foil is proposed in Japanese patent laid-open publication No. 6-13633.
In the solar cell panel or solar cell sheet described in Japanese patent laid-open publication No. 9-162434, a mesh is constructed from insulating warp filaments and first and second woof filaments on which different metal coating films are formed; furthermore, numerous spherical elements in which a diffusion layer is formed on the surface of a p type spherical single crystal of silicon are manufactured, these spherical elements are disposed in the respective eyes of the abovementioned mesh, the first woof filaments are connected to the diffusion layers, the second woof filaments are connected to the spherical single crystal of silicon, and these elements are sealed with synthetic resin.
In the case of this solar cell panel, the manufacture of the mesh having a special structure is not easy, and the manufacturing cost is also high. Furthermore, since the spherical elements do not have electrodes, the first woof filaments must be coated with a substance that does not form an alloy with the p type spherical elements, and the second woof filaments must be coated with a substance that forms an alloy with the p type spherical elements so that non-rectified contact is possible. Accordingly, there are restrictions on the substances that are respectively used to coat the first and second woof filaments, so that it is difficult to lower the manufacturing cost. The second woof filaments and the p type spherical elements are heated at the time of alloy formation; however, since there is a danger that the donor of the n type diffusion layer formed in the surface will be diffused by heating, there are also restrictions on the substances that can be used as a donor, and control of the heating temperature is also difficult.
In the photo power generating panel described in Japanese patent laid-open publication No. 2001-210834, numerous spherical elements are manufactured in which a diffusion layer is formed in the surface of a p type or n type spherical crystalline silicon, these spherical elements are inserted into numerous holes formed in a printed board, printed wiring is connected to the diffusion layers of the numerous spherical elements, the diffusion layers of the numerous spherical elements on the side of the back surface of the printed board are subsequently removed by etching, the printed board on which the numerous spherical elements have been incorporated is placed on top of another printed board, and the spherical crystals of the respective spherical elements are connected to the printed wiring. However, in the case of such a photo power generating panel, since the numerous spherical power generating elements are connected in parallel, the electromotive force of a single photo power generating panel cannot be increased, and since two printed boards are used, the cost of parts and cost of assembly are high, so that the manufacturing cost of the photo power generating panel is also increased. Since two printed boards are used, the panel tends to have a high rigidity, so that it is difficult to construct a photo power generating panel with flexibility. In all of the abovementioned panels, the gap between the electrodes is reduced as the spherical diameter is reduced, so that it is difficult to reduce the size of the panel. Furthermore, since the spherical light emitting elements do not have independent electrodes, individual testing for defective parts prior to the connection of the elements to the printed wiring is impossible.
Objects of the present invention are, to provide a light receiving or light emitting device in which numerous particulate semiconductor elements each of which has a pair of independent electrodes formed like a spot on both end parts are connected by means of conductive wire members, to provide a light receiving or light emitting device with flexibility, to provide a light receiving or light emitting device in which there are few restrictions on the material used as the conductive wire member, and to provide a light receiving or light emitting device in which numerous particulate semiconductor elements can be connected by parallel connections or series-parallel connections.